I like my display on full brightness with a dark colorscheme when coding. When switching from full screen Vim to a browser window or a terminal, the display settings make the screen far too bright. To avoid that, the following procedure sets the screen brightness to full when Vim gains focus, then sets the screen to half brightness when Vim loses focus.

Tip could be improved if the tool were improved to report the current brightness setting so it can be restored. Also you probably only want this to happen if in fullscreen mode, so could possibly be improved there (if there is a way for Vim to detect it is full screened).